1. Field of the Invention
This invention relates to electrical and mechanical apparatus for controlling a throttle plate of a carburetor of an internal combustion engine in response to loss of traction by a driving wheel, or other similar condition, and more particularly, to improvements in such throttle control devices that provides rapid and accurate throttle control, and can be accomplished in a cost effective manner.
2. Relevant Background
Recently, the automotive industry has begun implementing a so-called traction control feature available on modern vehicles. Briefly, a typical traction control device operates to adjust the position of a throttle plate of the carburetor of the internal combustion engine when loss of traction of one of the driving wheels of the vehicle on which the device is implemented loses traction with the road surface. Typically, a second or supplemental throttle plate is employed in the carburetor, and is operated by a stepper motor. The stepper motor is operated in response to a signal indicating that traction is lost by applying stepping pulses to the stepper motor to close the throttle until traction is regained. At the time traction is regained, pulses are applied to the stepper motor in an appropriate way to move the motor in the opposite direction to reopen the throttle.
One of the most serious drawbacks in presently available traction control systems is in their lack of cost effectiveness. The stepper motors are typically motors having 96 poles to enable a reasonable throttle position accuracy to be realized. Such motors are inherently expensive in and of themselves, and require sophisticated circuitry to properly operate.
In addition, the stepper motor systems typically used are open loop, deriving for their positional accuracy from the inherent nature of a stepper motor which moves a predetermined increment with each step. Consequently, for example, if a throttle is desired to be moved between two known positions, a number of stepping pulses are applied to the motor sufficient to move the motor from the first to second position, without a requirement for positional feedback from the throttle. However, it can be seen that if for any reason one or more of the stepping pulses is ineffective to move the stepping motor, the entire system accuracy is lost. Typically most systems are over-designed to compensate for this, and therefore are more expensive to realize.
Moreover, the accuracy of presently used stepper motor systems depends upon the increments in which the motor can be stepped. The stepper motors generally cannot be positioned at positions in between steps. This shortcoming is one of the reasons that stepper motors used in such environments have typically large numbers of poles (for instance 96), in order to increase the positional resolution that can be achieved by the particular motor.